netdev - Re: [PATCH] net: phy: realtek: Dummy IRQ calls for RTL8366RB

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Date:   Sun, 24 Feb 2019 01:07:27 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        netdev <netdev@...r.kernel.org>,
        Heiner Kallweit <hkallweit1@...il.com>
Subject: Re: [PATCH] net: phy: realtek: Dummy IRQ calls for RTL8366RB

> They are handled by the irqchip mask/unmask inside
> the RTL8366RB, see:
> drivers/net/dsa/rtl8366rb.c
> 
> So as soon as the phy core request the threaded IRQ
> the irqchip will deal with this business on its own.
> 
> How exactly the RTL8366RB IRQ machine looks inside
> I doubt even Realtek knows themselves, but from
> my experiements, they seem all edge triggered,
> and the irq will be raised every time an edge occurse
> (such as inserting or removing the cable). The "ACK"
> happens in hardware when we read the status register
> in the nested interrupt handler in rtl8366rb_irq() so no
> further registers need to be accessed.

Hi Linus

Thanks for the explanation. So dummy functions are fine in this case.

However, in general, i don't think dummy functions will work for a PHY
driver, and may lead to interrupt storms. So it might be better to
have them in the driver, not the core, with comments about why they
are safe.

     Andrew